JP6951038B2 - Steel structure and construction method of steel structure - Google Patents

Description

The present invention relates to a steel structure and a method for constructing a steel structure, and more particularly to a steel structure and a method for constructing a steel structure capable of improving durability against salt damage.

There is known a technique for suppressing corrosion of a steel material due to the adhesion of moisture by applying an anticorrosive coating to the surface of the steel material (constituent body) constituting the steel structure. For example, Patent Document 1 discloses a steel structure in which a rust preventive layer composed of an anticorrosive base layer, a polyimide layer, an undercoat layer, an intermediate coat layer, and a topcoat layer is formed on the surface of a steel material. According to this steel structure, the rust preventive layer improves the rust preventive effect of the steel material and can improve the durability of the steel structure.

Japanese Unexamined Patent Publication No. 2015-205260 (for example, paragraphs 0029 to 0031, FIGS. 2 and 3)

However, with the above-mentioned conventional technique, the corrosion resistance of the anticorrosive coating film (rust preventive layer) against salt is insufficient, and when a steel structure is constructed in an environment where flying salt or seawater adheres, the salt content is the anticorrosive coating. Corrosion of the constituent (steel material) is promoted by adhering to the film and permeating corrosive ions such as chloride ions into the coating film. Further, there is a problem that the corrosion of the constituent body is promoted by the chloride by spraying not only the flying salt and seawater but also the antifreezing agent and the snow melting agent containing chloride.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a steel structure and a method for constructing the steel structure, which can improve the durability against salt damage.

In order to achieve this object, the steel structure of the present invention is formed on a structure constructed in an environment where flying salt or seawater adheres, and on the surface of the structure, and a multi-layer coating film by anticorrosion coating. The anticorrosion coating film comprises a salt damage suppressing layer formed as a layer on the most surface layer side thereof, and the salt damage suppressing layer comprises a cross-linking agent, a urethane bond, and a urethane bond. a fluorine resin having a polysiloxane bond formed by water-repellent coating that will be contained, the salt damage suppression layer is formed at a portion in the rain line in at least the structure.
The method for constructing a steel structure of the present invention is formed on a structure constructed in an environment to which flying salt or seawater adheres, and on the surface of the structure, and is also formed as a multi-layer coating film by anticorrosion coating. and anticorrosive coating film, the construction method of steel structures comprising, forming a construction step for building the structure, before or after the construction process, the most surface layer side to salt damage suppression layer of the anticorrosive coating film coating comprising a step, wherein the salt damage suppressing layer, a crosslinking agent, a fluorine resin having a urethane bond and a polysiloxane bond formed by water-repellent coating that will be contained, the salt damage suppressing layer deposition in at least the structure It is formed at the site in the line.

According to the method for constructing the steel structure according to claim 1 and the method for constructing the steel structure according to claim 6, the anticorrosion coating film is formed as the layer on the most surface layer side thereof and also suppresses salt damage formed by the water-repellent paint. Since the layer is provided, even if salt adheres to the surface of the anticorrosion coating film, the salt is easily washed away by the water-repellent action of the salt damage suppressing layer (for example, washing with rainwater). Therefore, it is possible to suppress the accumulation of salt on the surface of the anticorrosion coating film. Further, even if the salt content adhering to the surface of the anticorrosion coating film is deliquescent to generate chloride ions, the invasion of the chloride ions into the constituent side can be suppressed by the water-repellent action of the salt damage suppressing layer. Therefore, it is possible to prevent the structure from being corroded by salt, which has the effect of improving the durability of the steel structure against salt damage.

Further, according to the steel structures and claim 6 construction method steel structures according to claim 1, salinity suppressing layer, a fluorine resin having a urethane bond and a polysiloxane bond and cross-linking agent is Ru contained repellent Runode formed by aqueous coating composition, it is possible to improve the water repellency of salt damage suppression layer. As a result, the salt adhering to the anticorrosion coating film is more easily washed away, so that the accumulation of salt on the surface of the anticorrosion coating film can be more reliably suppressed. Therefore, since the structure can be more reliably suppressed from being corroded by salt, there is an effect that the durability of the steel structure against salt damage is improved. Further, since the salt damage suppressing layer is formed on the structure located in the rain line, there is an effect that the salt content can be suppressed from staying on the surface of the anticorrosion coating film even in a portion where it cannot be expected to be washed away by rainwater.

According to the steel structure according to claim 2, in addition to the effect of the steel structure according to claim 1, since the salt damage suppressing layer is formed at least in the uneven portion of the structure, the corrosion resistance of the structure against salt is improved. improves. That is, the film thickness of the anticorrosion coating film (on the lower layer side of the salt damage suppressing layer) tends to be thin on the uneven portion of the structure, and the corrosion resistance to salt content is reduced accordingly. On the other hand, according to the steel structure according to claim 3, the corrosion resistance of the concavo-convex portion of the structure can be enhanced by forming the salt damage suppressing layer on the anticorrosion coating film in the concavo-convex portion of the structure. ..

As a result, for example, it is possible to suppress corrosion in the uneven portion of the structure and reduce the number of times of repainting, so that there is an effect that the life cycle cost of the steel structure can be reduced.

According to the steel structure according to claim 3, in addition to the effect of the steel structure according to claim 1 or 2, the following effects are exhibited. The salt damage control layer is formed at least at a site where contact with rainwater is blocked in the constituent body. Here, since it is difficult for the rainwater to wash away the portion where the contact with the rainwater is blocked, salt is likely to be deposited on the surface of the anticorrosive coating film, and the deposited salt is deliquescent to form the structure. It becomes easy to corrode.

On the other hand, according to the steel structure according to claim 3, by forming a salt damage suppressing layer at a portion where contact with rainwater is blocked, the water repellent action makes it easier for salt to be washed away (for example,). Rinse with the blowing wind). Further, even when the salt adhering to the surface of the anticorrosion coating film is deliquescent, the deliquescent salt flows due to the water-repellent action of the salt damage suppressing layer, so that the salt content can be suppressed from staying on the surface of the anticorrosion coating film. .. Therefore, even in a portion that cannot be expected to be washed away by rainwater, the corrosion resistance of the structure to salt can be enhanced, which has the effect of improving the durability of the steel structure against salt damage.

According to the steel structure according to claim 4, in addition to the effect of the steel structure according to any one of claims 1 to 3, the structure is configured as a bridge, so that the structure constituting the bridge Corrosion resistance to salt can be enhanced at the site where contact with rainwater is blocked. This has the effect of reducing the life cycle cost of the bridge, for example, because the number of times the paint is repainted at the portion of the bridge where contact with rainwater is blocked can be reduced.

According to the steel structure according to claim 5, in addition to the effect of the steel structure according to any one of claims 1 to 4, a chloride ion adsorbent is contained in the salt damage suppressing layer, so that the anticorrosion coating film is used. Chloride ions generated by deliquescent of salt adhering to the surface of the above can be adsorbed on the chloride ion adsorbent. As a result, it is possible to prevent the salt (chloride ion) adhering to the surface of the anticorrosion coating film from invading the lower layer side than the salt damage suppressing layer. Therefore, even in a portion that cannot be expected to be washed away by rainwater, the corrosion resistance of the structure to salt can be enhanced, which has the effect of improving the durability of the steel structure against salt damage.

(A) is a schematic view of a bridge according to an embodiment of the present invention, and (b) is a cross-sectional view of the bridge on the line Ib-Ib of FIG. 1 (a). (A) is a partially enlarged perspective view of a bridge girder, and (b) is a partially enlarged cross-sectional view of a bridge showing a cross section of an anticorrosion coating film. It is a table which shows the specification of a painting process. (A) is a table showing the result of the verification test when the test piece is vertically installed outdoors, and (b) is a table showing the result of the verification test when the test piece is vertically installed indoors. (C) is a table showing the results of the verification test when the test piece is horizontally installed outdoors.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, the overall configuration of the bridge 1 will be described with reference to FIGS. 1 and 2. 1 (a) is a schematic view of the bridge 1 according to the embodiment of the present invention, and FIG. 1 (b) is a cross-sectional view of the bridge 1 on the line Ib-Ib of FIG. 1 (a). FIG. 2A is a partially enlarged perspective view of the bridge girder 21, and FIG. 2B is a partially enlarged cross-sectional view of the bridge 1 showing a cross section of the anticorrosion coating film 5. In addition, in FIG. 1, in order to simplify the drawing, a part of the bridge 1 is omitted and is schematically illustrated.

As shown in FIG. 1 (a), the bridge 1 includes a pair of abutments 3 that support the upper structure 2 and both ends of the upper structure 2 in the bridge axial direction (left-right direction in FIG. 1 (a)). It is configured as a steel bridge provided with a pier 4 for supporting the superstructure 2 between the abutments 3 of the above.

As shown in FIG. 1 (b), the superstructure 2 is arranged below the deck 20, the bridge girder 21 (main girder) arranged below the deck 20, and below the bridge girder 21. , A support 22 for supporting the deck 20 and the bridge girder 21.

A roadway, a sidewalk, a railroad track, or the like (not shown) is arranged on the upper surface of the deck 20 (the upper surface of FIG. 1B), and the deck 20 is supported by the bridge girder 21. The bridge girder 21 has a flat plate-shaped web 21a extending along the bridge axis direction (vertical direction on the paper surface in FIG. 1B) and a direction perpendicular to the bridge axis from the upper and lower ends of the web 21a (FIG. 1 (b). ) Is formed as a steel I girder having a flat upper flange 21b and a lower flange 21c overhanging in the left-right direction).

As shown in FIG. 2A, in the bridge girder 21, the ends of the bridge girders 21 adjacent to each other in the bridge axis direction are butted against each other, and the butted portions are connected via a plurality of splicing plates 23 to 25. The splicing plates 23 to 25 are steel plate-like bodies having a vertically long rectangular shape or a horizontally long rectangular shape when viewed from the front. The 25 (25a, 25b) sandwiches the upper flange 21b and the lower flange 21c in the plate thickness direction, respectively.

A plurality of insertion holes (not shown) are bored at the ends of the bridge girder 21 in the direction of the bridge axis in a grid-like arrangement in the vertical and horizontal directions, and a plurality of insertion holes are provided in the splicing plates 23 to 25 of the bridge girder. Each is drilled in an arrangement corresponding to the insertion holes of 21. Therefore, by arranging the splicing plates 23 to 25 at the specified positions with respect to the bridge girder 21, the insertion holes of the bridge girder 21 and the insertion holes of the splicing plates 23 to 25 are communicated with each other, and the bolt B can be inserted. Will be done. As a result, the splicing plates 23 to 25 are fastened to the bridge girder 21 by bolts B and nuts N, so that the bridge girders 21 are connected to each other in the bridge axial direction via the splicing plates 23 to 25.

Further, a plurality of bridge girders 21 (four in the present embodiment) are arranged in the direction perpendicular to the bridge axis (see FIG. 1 (b)). Of the plurality of bridge girders 21, a part of the pair of bridge girders 21 located at both ends in the direction perpendicular to the bridge axis is predetermined from the vertical line V passing through the tip (lower end) of the deck 20 in the direction perpendicular to the bridge axis. Formed located inside the rain line (the line shown by the virtual line L1 in FIG. 1B; hereinafter referred to as “rain line L1”) inclined at an angle θ (approximately 45 ° in the present embodiment). Will be done. The region inside the rain line L1 (inside the rain line) is a region where rainwater is unlikely to be applied under normal rainfall conditions.

The bearing 22 is interposed between the pier 4 (abutment 3) and the superstructure 2, and transmits the load acting between the pier 4 (abutment 3) and the superstructure 2 (deck 20 and the bridge girder 21) to each other. Since it is a member to be used and a known configuration can be adopted, detailed description thereof will be omitted.

The pier 4 includes a column portion 40 erected above the foundation (not shown) and a beam portion 41 projecting from the upper end of the column portion 40 in a direction perpendicular to the bridge axis, and serves as an overhang type pier made of steel. Formed (as steel piers).

A part of the column portion 40 is inclined at a predetermined angle θ (approximately 45 ° in the present embodiment) from the vertical line V passing through the tip (lower end portion) of the beam portion 41 in the direction perpendicular to the bridge axis. It is formed located inside the rain line (the line shown by the virtual line L2 in FIG. 1B; hereinafter referred to as “rain line L2”). Similar to the rain line L1 described above, the region inside the rain line L2 (inside the rain line) is a region where rainwater is unlikely to be applied under normal rainfall conditions.

The beam portion 41 is a portion for supporting the superstructure 2, and the superstructure 2 is supported by the abutment 3 and the pier 4 by placing the bearing 22 on the upper surface of the beam 41 and the abutment 3. ..

Here, the bridge 1 is constructed in an environment to which flying salt or seawater adheres, and the surface of the part made of steel in the components (superstructure 2, abutment 3 and pier 4) constituting the bridge 1 is protected from corrosion. The coating film 5 is formed (see FIG. 2B). In the present embodiment, the anticorrosion coating film 5 is formed on each member of the bridge girder 21, the splicing plate 23 to 25, the bolt B, the nut N, the column portion 40, and the beam portion 41. Each of these members will be described simply as a "constituent".

The anticorrosion coating film 5 includes an anticorrosion base layer (not shown) formed by applying a mist coat (coating a paint made of an epoxy resin) to a coating film formed by coating an inorganic zinc rich paint. The undercoat layer 50 formed on the anticorrosion base layer, the intermediate coat layer 51 formed on the undercoat layer 50, the topcoat layer 52 formed on the intermediate coat layer 51, and the topcoat thereof. A salt damage suppressing layer 53 formed on the layer 52 is provided.

The undercoat layer 50 is formed by applying an undercoat paint made of an epoxy resin, and the intermediate coat layer 51 is an intermediate coat paint made of an epoxy resin (an intermediate coat paint used when the topcoat paint is made of a fluororesin). It is formed by painting. Further, the topcoat layer 52 is formed by applying a topcoat paint made of a fluororesin. That is, the undercoat layer 50, the intermediate coat layer 51, and the topcoat layer 52 are coating films formed by heavy-duty anticorrosion coating.

The salt damage suppressing layer 53 is a coating film for preventing salt adhering to the anticorrosion coating film 5 from invading the constituent side (lower layer side than the salt damage suppressing layer 53), and is water repellent on the surface of the topcoat layer 52. It is formed by applying paint. This water-repellent paint is a paint containing a fluororesin having a urethane bond and a polysiloxane bond and a cross-linking agent, and the fluororesin is also contained in the salt damage suppressing layer 53.

That is, since the salt damage suppressing layer 53 is formed as the most surface layer side layer of the anticorrosion coating film 5 and also as a coating film having a water repellent action, flying salt adheres to the surface of the anticorrosion coating film 5. Even so, the water repellency of the salt damage suppressing layer 53 makes it easier for the salt to be washed away. That is, the salt adhering to the anticorrosive coating film 5 is easily washed away by rainwater, and the accumulation of salt on the surface of the anticorrosive coating film 5 can be suppressed, so that the constituent body can be prevented from being corroded by the salt.

Further, even if the salt content adhering to the surface of the anticorrosion coating film 5 is deliquescent to generate chloride ions, the invasion of the chloride ions into the constituent side can be suppressed by the water repellent action of the salt damage suppressing layer 53. Therefore, even when the bridge 1 is constructed in an environment where flying salt or seawater adheres, the durability of the bridge 1 against salt damage is improved.

Further, since the fluororesin having a urethane bond and a polysiloxane bond is contained in the salt damage suppressing layer 53, the water repellency of the salt damage suppressing layer 53 can be enhanced. As a result, the salt adhering to the anticorrosion coating film 5 is more easily washed away, so that the accumulation of salt on the surface of the anticorrosion coating film 5 can be more reliably suppressed. Therefore, since the structure can be more reliably suppressed from being corroded by salt, the durability of the bridge 1 against salt damage is improved.

Here, the structure includes a connecting portion between the web 21a and the upper flange 21b (lower flange 21c), an overhanging portion of the upper flange 21b (lower flange 21c), the head of the bolt B, the nut N, and the splicing. Concavo-convex portions (corners and corners in each member) are formed by the plates 23 to 25 and the like.

In these uneven portions, the film thickness of the coating film (undercoat layer 50, intermediate coating layer 51, and topcoat layer 52) by heavy anticorrosion coating tends to be thin, and the corrosion resistance of the anticorrosion coating film 5 to salt content is lowered. On the other hand, according to the bridge 1 of the present embodiment, since the uneven portion of the structure is covered with the salt damage suppressing layer 53, the corrosion resistance of the uneven portion of the structure, which tends to have low corrosion resistance to salt, is enhanced. Can be done. As a result, corrosion on the uneven portion of the structure can be suppressed, so that, for example, the number of times of repainting on the uneven portion of the structure can be reduced. Therefore, the life cycle cost of the bridge 1 can be reduced.

In addition, a portion is formed in the structure so that contact with rainwater is blocked. The portion where contact with rainwater is blocked is a structure located within the rain line on the inner side in the direction perpendicular to the bridge axis with respect to the rain lines L1 and L2 described above (see FIG. 1 (b)).

Since the structure located within the rain line is unlikely to be washed away by rainwater, if salt adheres to the surface of the anticorrosion coating film 5, salt tends to remain (deposit) on the surface of the anticorrosion coating film 5. .. When the salt content remaining on the surface of the anticorrosive coating film 5 is deliquescent, the constituents are easily corroded by the chloride ions generated by the deliquescent.

On the other hand, according to the bridge 1 of the present embodiment, the salt content adheres to the surface of the anticorrosion coating film 5 by forming the salt damage suppressing layer 53 on the anticorrosion coating film 5 of the structure located in the rain line. Even so, it is easily washed away by the water-repellent action of the salt damage suppressing layer 53. That is, for example, even if the flying salt containing water adheres to the surface of the anticorrosion coating film 5, it tends to flow off from the surface of the anticorrosion coating film 5 due to the weight of the flying salt or the blowing wind. Further, even if the salt deposited on the surface of the anticorrosion coating film 5 is deliquescent, the deliquescent salt is easily washed away by the water-repellent action of the salt damage suppressing layer 53. Therefore, it is possible to prevent salt from staying on the surface of the anticorrosion coating film 5 even in a portion that cannot be expected to be washed away by rainwater.

Further, even if chloride ions are generated by deliquescent of the salt adhering to the surface of the anticorrosion coating film 5, the invasion of the chloride ions into the constituent side can be suppressed by the water repellent action of the salt damage suppressing layer 53. Therefore, the corrosion resistance of the structure to salt content can be increased, and the durability of the bridge 1 against salt damage is improved. Further, by increasing the corrosion resistance of the structure located in the rain line of the bridge 1 to the salt content, for example, the number of times of repainting of the structure can be reduced, so that the life cycle cost of the bridge 1 can be reduced.

Here, even if the structure is located within the rain line, the salt content adhering to the horizontally inclined surface (for example, the vertical surface) (for example, the salt content adhering to the surface of the web 21a or the lower surface of the beam portion 41). ), Fluidity is generated by deliquescent, and it is easy to run off due to its own weight (remaining on the surface of the anticorrosion coating film 5 is suppressed).

On the other hand, adhered salt is likely to accumulate on a substantially horizontal surface (for example, the lower surface of the upper flange 21b, the upper surface of the lower flange 21c, the upper surface of the beam portion 41, etc.) in the structure located within the rain line. That is, the salt adhering to the substantially horizontal surface of the structure located in the rain line is likely to remain on the surface of the anticorrosive coating film 5 without flowing down due to its own weight even if fluidity is generated by deliquescent. The body is prone to corrosion.

On the other hand, according to the bridge 1 of the present embodiment, since the salt damage suppressing layer 53 is formed on a substantially horizontal surface of the structure located in the rain line, the deliquescent salt content is the surface of the anticorrosion coating film 5. Even if it remains in the salt damage suppressing layer 53, the water repellent action of the salt damage suppressing layer 53 can suppress the invasion of salt (chloride ion) into the lower layer side (constituent side) of the salt damage suppressing layer 53. Therefore, even in a portion that cannot be expected to be washed away by rainwater, the corrosion resistance of the constituent body to salt can be enhanced, so that the durability of the bridge 1 against salt damage is improved. A substantially horizontal surface is defined as a surface having a gradient of less than 3% in the horizontal direction.

Next, a method of constructing the bridge 1 will be described with reference to FIG. FIG. 3 is a table showing the specifications of the painting process. The method for constructing the bridge 1 in the present embodiment includes a coating step of forming the anticorrosion coating film 5 by applying coating to the constituent body (steel material), and a construction process of constructing the bridge 1 after the coating step.

That is, in the present embodiment, the parts to be joined at the site in the construction process (for example, at the construction site of the bridge 1, the parts where the bridge girders 21 are connected by the splicing plates 23 to 25, the bolts B and the nuts N, etc.). Except for, the anticorrosion coating film 5 of the constituent is formed by factory coating.

As shown in FIG. 3, in the painting process, an inorganic zinc rich paint is applied to the surface of a steel material that has been subjected to base material adjustment by blasting (the base material adjustment standard conforms to ISO Sa2.5) with a film thickness of 75 μm. .. By applying a mist coat to the surface of the inorganic zinc rich paint (painting a paint made of epoxy resin to seal the holes), an anticorrosion base layer is formed.

Next, the undercoat layer 50 (see FIG. 2B) is formed by applying an undercoat paint made of an epoxy resin to the surface of the anticorrosion base layer with a film thickness of 120 μm. An intermediate coating material (intermediate coating material for fluororesin coating) made of epoxy resin is applied to the surface of the undercoat layer 50 to form an intermediate coating layer 51 with a film thickness of 30 μm, and the surface of the intermediate coating layer 51 is formed. In addition, a topcoat paint made of a fluororesin is applied with a film thickness of 25 μm to form a topcoat layer 52.

Then, the surface of the topcoat layer 52 (that is, the most surface layer side of the anticorrosion coating film 5) is coated with a water-repellent paint with a film thickness of 15 μm to form the salt damage suppressing layer 53. As described above, the water-repellent paint constituting the salt damage suppressing layer 53 is a paint containing a fluororesin having a urethane bond and a polysiloxane bond and a cross-linking agent.

By this painting step, an anticorrosion coating film 5 is formed on the surface of the structure, and after this painting step, a construction step of constructing the bridge 1 by the structure on which the anticorrosion coating film 5 is formed is performed. The construction process is a process of constructing the bridge 1 in an environment where flying salt or seawater adheres using the structure (steel material) painted by the painting process.

In the construction process, a vent (gantry) is assembled as temporary equipment between the pier 3 and the pier 4 (see FIG. 1 (a)), and the erection girder (bridge girder 21) lifted by a crane is assembled with the pier 4 (pier 3) and the vent. The main girder is formed by erection between the erection girder and between the vents and connecting the erection girders in order. After that, a horizontal girder is erected between the main girders arranged side by side, a grid-like structure (main girder and horizontal girder) is formed, and then the floor slab 20 is arranged to construct the bridge 1. Will be done.

According to the above method for constructing the bridge 1, the anticorrosion coating film 5 is formed on the constituent body constituting the bridge 1, and the salt damage suppressing layer 53 is formed on the most surface layer side of the anticorrosion coating film 5. .. Since the salt damage suppressing layer 53 is formed as a coating film by coating with a water repellent paint, even if flying salt or seawater adheres to the surface of the anticorrosion coating film 5, the salt content is washed away by the water repellency of the salt damage suppressing layer 53. It will be easier. As a result, it is possible to suppress the accumulation of salt on the surface of the anticorrosive coating film 5, and thus it is possible to prevent the constituents from being corroded by the salt. Therefore, even when the bridge 1 is constructed in an environment where flying salt or seawater adheres, the durability of the bridge 1 against salt damage is improved.

Next, with reference to FIG. 4, a verification test in which the amount of salt adhering to the salt damage control layer 53 is measured will be described. FIG. 4A is a table showing the results of the verification test when the test pieces A and B are vertically installed outdoors, and FIG. 4B is a table when the test pieces A and B are vertically installed indoors. It is a table showing the result of the verification test, and FIG. 4C is a table showing the result of the verification test when the test pieces A and B are horizontally installed outdoors.

The outdoor is an environment in which the test pieces A and B are directly exposed to rainfall, and the indoor is an environment in which the test pieces A and B are not subject to rainfall and is well-ventilated. In addition, vertical installation means that the test pieces A and B are erected along the vertical direction (the plate thickness direction is directed to the horizontal direction), and horizontal installation means that the test pieces A and B are placed in the horizontal direction. It is in a state of being laid down along (the plate thickness direction is directed to the vertical direction).

In this verification test, a test piece formed from a steel material (SS400) into a flat plate shape (500 mm × 500 mm × 4.5 mm in the present embodiment) was used. With respect to this test piece, a test piece A in which a coating film obtained by omitting the salt damage suppressing layer 53 from the above-mentioned anticorrosion coating film 5 was formed, and a test piece B in which a coating film of the same coating system as the above-mentioned anticorrosion coating film 5 was formed. I prepared.

The test piece B was coated with a water-repellent paint containing a fluororesin having a urethane bond and a polysiloxane bond and a cross-linking agent to form a salt damage suppressing layer 53.

After exposing these test pieces A and B to an environment where flying salt adheres for a predetermined period of time, the amount of salt (mg / m) adhering to one square meter of the surface of the coating film is determined in each of the test pieces A and B, respectively. Five points were measured, the average value was calculated, and the average values were compared to calculate the reduction rate of the amount of adhering salt. In the following description, the unit of the amount of attached salt (mg / square meter) will be omitted, and only the numerical values will be compared and described.

As shown in FIG. 4A, when the test pieces A and B are vertically installed outdoors for 3 months, the amount of adhering salt (average value of 5 points) of the test piece A in which the salt damage suppression layer 53 is not formed is 11. On the other hand, the amount of adhering salt of the test piece B on which the salt damage suppressing layer 53 is formed is 10.8, and the amount of adhering salt of the test piece B is 5. It was confirmed that the reduction was 3%.

That is, in the case of vertical installation outdoors, although the action of washing away the salt by rainwater occurs in both the test pieces A and B, the amount of adhering salt is smaller in the test piece B. It is considered that this is a result of the water-repellent action of the salt damage suppressing layer 53 making it easier for the salt adhering to the surface of the coating film of the test piece B to be washed away. Therefore, by forming the salt damage suppressing layer 53 on the structure (that is, the portion where the action of washing away by rainwater occurs) located on the outside (outside the rain line) in the direction perpendicular to the bridge axis with respect to the rain lines L1 and L2 in the bridge 1, the salt damage suppressing layer 53 is formed. It is clear that the same remarkable effect as this test result can be obtained.

As shown in FIG. 4B, when each of the test pieces A and B was vertically installed indoors for 3 months, the amount of adhering salt of the test piece A was 190.8, whereas the amount of adhering salt of the test piece B was 190.8. The amount was 172.7, and it was confirmed that the amount of attached salt of test piece B was reduced by 9.5% with respect to the amount of attached salt of test piece A.

That is, when installed indoors, the effect of washing away salt by rainwater does not occur in both test pieces A and B, but the amount of adhering salt is smaller in test piece B. This is because even if the flying salt containing water adheres to the surface of the coating film of the test piece B, it is easily washed away by the water-repellent action of the salt damage suppressing layer 53, for example, by the blowing wind or the weight of the flying salt. It is believed that there is. Further, it is considered that even when the salt content adhering to the surface of the coating film of the test piece B is deliquescent to generate fluidity, the water-repellent action of the salt damage suppressing layer 53 makes it easier to run off.

Therefore, by forming the salt damage suppressing layer 53 on the structure located in the rain line of the bridge 1 (that is, the portion where the action of washing away by rainwater is unlikely to occur), the same remarkable effect as this test result can be obtained. Is clear.

As shown in FIG. 4C, when each of the test pieces A and B was horizontally installed outdoors for 12 months, the amount of adhering salt of the test piece A was 34.6, whereas the amount of adhering salt of the test piece B was 34.6. The amount was 19.5, and it was confirmed that the amount of attached salt of test piece B was reduced by 43.6% with respect to the amount of attached salt of test piece A.

That is, although the salt content is washed away by rainwater when installed outdoors, the salt content is unlikely to flow off from the coating film surface due to its own weight when installed horizontally. In this case, it is considered that the above result was obtained because the salt content of the test piece B was easily washed away by the blowing wind due to the water-repellent action of the salt damage suppressing layer 53. Therefore, it is clear that the same remarkable effect as this test result can be obtained by forming the salt damage suppressing layer 53 on a substantially horizontal surface of the structure located outside the rain line in the bridge 1.

Although the present invention has been described above based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is easy that various modifications and improvements can be made without departing from the spirit of the present invention. It can be inferred from. For example, the film thickness of the coating film in the above embodiment is an example and can be set as appropriate.

In the above embodiment, the description of the step of forming the salt damage suppressing layer 53 at the site to be attached to the site in the construction process and the step of forming the salt damage suppressing layer 53 when the constituent body is painted on the site is omitted. In any of the steps, the salt damage suppressing layer 53 may be formed on the most surface layer side of the anticorrosion coating film (that is, on the final topcoat layer).

Therefore, for example, when painting a portion that has been field-bonded (field-welded), the salt damage suppression layer 53 may be formed on the topcoat layer formed by the painting, and the constituent body is painted on-site. In this case, the salt damage suppressing layer 53 may be formed on the topcoat layer formed by the on-site coating. That is, if the structure is such that the salt damage suppressing layer 53 is formed on the outermost surface layer side of the anticorrosion coating film, the coating step for forming the salt damage suppressing layer 53 may be performed before the construction process or after the construction process. You may.

Further, instead of forming the salt damage suppressing layer 53 on the topcoat layer, the topcoat layer and the salt damage suppressing layer 53 may be formed in the same layer. That is, the topcoat layer may be formed by a water-repellent paint (for example, one containing a fluororesin having a urethane bond and a polysiloxane bond and a cross-linking agent).

In the above embodiment, the bridge 1 has been described as an example as a steel structure (a structure composed of the structure), but the present invention is not necessarily limited to this. For example, any other structure may be used as long as it is a structure constructed in an environment to which flying salt or seawater adheres. Other structures include, for example, steel towers, houses (buildings, factories, warehouses, etc.), parking lots, fences, roofs (eg, structures that support nets to prevent flying balls from golf courses into highways). , Water gates, undulating gates, plants (pipelines), gas tanks, wind power propeller towers, etc. are exemplified.

In the above embodiment, the case where the salt damage suppressing layer 53 is formed on all of the anticorrosion coating film 5 of the structure made of steel material has been described, but the present invention is not necessarily limited to this. For example, the salt damage suppressing layer 53 is formed only on the constituent body located in the rain line, the uneven portion in the constituent body, or the horizontal plane in the constituent body, and the salt damage suppressing layer 53 is not formed in the other constituent parts. It may be formed.

In this case, it is preferable to omit the salt damage suppression layer 53 of the structure located outside the rain line, and the surface of the structure that is located outside the rain line and is inclined with respect to the horizontal direction. It is more preferable to omit the salt damage suppressing layer 53. That is, since the structure located outside the rain line has an action of washing away salt by rainwater, the corrosion resistance of the structure to salt is formed by not forming the salt damage suppressing layer 53 in the structure located outside the rain line. The cost for forming the salt damage suppression layer 53 can be reduced while ensuring the above.

Further, a structure located outside the rain line, and a surface of the structure that is inclined with respect to the horizontal direction, more effectively flushes salt with rainwater, so that salt damage is suppressed in such a surface. By forming the layer 53 non-forming, it is possible to reduce the cost for forming the salt damage suppressing layer 53 while more reliably ensuring the corrosion resistance of the constituent body against salt.

In the above embodiment, the case where the salt damage suppressing layer 53 contains a fluororesin having a urethane bond and a polysiloxane bond has been described, but the present invention is not necessarily limited to this. For example, it is more preferable that the salt damage suppressing layer 53 contains a chloride ion adsorbent. As an example of the chloride ion adsorbent, nitrite-type hydrocarmite (composite hydroxide of calcium and aluminum) configured as a metal composite hydroxide is exemplified. In this case, a salt damage suppressing layer is used with a water-repellent coating material containing a fluorine resin having a urethane bond and a polysiloxane bond, a cross-linking agent, and a chloride ion adsorbent (for example, nitrite-type hydrocarbimite). 53 may be formed.

That is, since the chloride ion adsorbent is contained in the salt damage suppressing layer 53, the chloride ion generated by deliquescent of the salt adhering to the surface of the anticorrosion coating film 5 can be adsorbed by the chloride ion adsorbent. .. Therefore, it is possible to prevent the salt (chloride ion) adhering to the surface of the anticorrosion coating film 5 from invading the lower layer side (constituent side) of the salt damage suppressing layer 53. Therefore, for example, even in a portion that cannot be expected to be washed away by rainwater, the corrosion resistance of the constituent body to salt can be enhanced, so that the durability of the bridge 1 against salt damage is improved.

Here, when the chloride ion adsorbent is contained in the salt damage suppressing layer 53, the strength of the salt damage suppressing layer 53 against contact with an object is lowered as compared with the case where the chloride ion adsorbent is not contained. On the other hand, since the structure located in the rain line has less contact with objects (for example, contact with a vehicle or a person crossing the bridge 1), peeling of the salt damage suppressing layer 53 due to contact with the objects is unlikely to occur. .. That is, by forming the salt damage suppressing layer 53 containing the chloride ion adsorbent on the anticorrosion coating film 5 of the constituent in the rain line, the salt damage suppressing layer is enhanced while improving the corrosion resistance of the constituent that cannot be expected to wash away rainwater. The durability of 53 itself can be ensured.

Further, the salt damage suppressing layer 53 containing the chloride ion adsorbent and the salt damage suppressing layer 53 containing no chloride ion adsorbent may be formed according to the site of the constituent. In this case, a salt damage suppressing layer 53 containing a chloride ion adsorbent is formed on the anticorrosive coating film 5 of the constituent located inside the rainline, and the anticorrosive coating film of the constituent located outside the rainline is formed. It is more preferable to form the salt damage suppressing layer 53 which does not contain the chloride ion adsorbent. That is, as described above, by forming the salt damage suppressing layer 53 containing the chloride ion adsorbent on the anticorrosion coating film 5 of the constituent body located in the rain line, the chloride ion invades the constituent body side. Can be suppressed.

On the other hand, the salt adhering to the anticorrosion coating film 5 of the constituent body located outside the rain line is dissolved in rainwater to generate chloride ions, but the chloride ions are washed away by the action of washing away with rainwater, so that the chloride ions are washed away. Even in the salt damage suppressing layer 53 which does not contain an adsorbent, it is possible to suppress the invasion of chloride ions into the constituent side.

Therefore, the salt damage suppressing layer 53 containing the chloride ion adsorbent is formed in the structure located inside the rain line, and the salt damage suppressing layer in which the chloride ion adsorbent is not contained in the structure located outside the rain line. By forming the layer 53, it is possible to improve the durability of the bridge 1 against salt damage, suppress the amount of the chloride ion adsorbent used, and reduce the construction cost of the bridge 1.

In the above embodiment, as an example of the portion where the salt damage suppressing layer 53 is formed, a substantially horizontal surface of the structure (a surface having a gradient of less than 3% in the horizontal direction) is exemplified, but the present invention is not necessarily limited to this. No. For example, the salt damage suppression layer 53 may be formed on a surface having a gradient of 3% or more in the horizontal direction.

1 Bridge (steel structure)
2 Superstructure (constituent)
3 Abutment (constituent)
4 Pier (construction)
5 Anticorrosion coating film 53 Salt damage suppression layer

Claims (6)

In a steel structure including a structure constructed in an environment to which flying salt or seawater adheres, and an anticorrosion coating film formed on the surface of the structure and formed as a multi-layer coating film by anticorrosion coating. ,
The anticorrosion coating film includes a salt damage suppressing layer formed as the layer on the most surface layer side thereof.
The salt damage suppressing layer, a crosslinking agent, a fluorine resin having a urethane bond and a polysiloxane bond formed by water-repellent coating that will be contained,
A steel structure characterized in that the salt damage suppressing layer is formed at least at a portion within a rain line in the structure. The steel structure according to claim 1, wherein the salt damage suppressing layer is formed at least on an uneven portion of the structure. The steel structure according to claim 1 or 2, wherein the salt damage suppressing layer is formed at least at a portion of the structure where contact with rainwater is blocked. The steel structure according to any one of claims 1 to 3, wherein the structure is configured as a bridge. The steel structure according to any one of claims 1 to 4, wherein the salt damage suppressing layer contains a chloride ion adsorbent. A steel structure comprising a structure constructed in an environment to which flying salt or seawater adheres, and an anticorrosion coating film formed on the surface of the structure and formed as a multi-layer coating film by anticorrosion coating. In the construction method
The construction process to build the structure and
As before or after the construction process, and a coating step of forming a most surface layer side to salt damage suppression layer of the anticorrosive coating film,
The salt damage suppressing layer, a crosslinking agent, a fluorine resin having a urethane bond and a polysiloxane bond formed by water-repellent coating that will be contained,
A method for constructing a steel structure, wherein the salt damage control layer is formed at least at a portion within a rain line in the structure.

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